End Disk

ABSTRACT

A plastic end disk for a hollow-cylindrical filter element has an end face plastic layer and a neighboring plastic layer. The end face plastic layer is transparent for infrared radiation. The neighboring plastic layer is absorbent for infrared radiation. The plastic end disk is connected to a folded filter medium in that the end face plastic layer is trans-irradiated with an infrared radiation source, wherein the infrared radiation is absorbed in the neighboring plastic layer so that a portion of the neighboring plastic layer and a portion of the end face plastic layer are completely melted. The infrared radiation source is removed and the filter medium is pressed into a melted area of the end face plastic layer. The filter medium is secured in the pressed-in position in the end face plastic layer until a fixed connection of filter medium and end face plastic layer has been formed.

TECHNICAL FIELD

The invention concerns a plastic end disk according to the preamble of claim 1. Moreover, the invention concerns a manufacturing method for a filter element by employing such an end disk according to the preamble of claim 8.

PRIOR ART

Such plastic end disks have the task to provide a usually circular ring-shaped surface into which a filter medium can be embedded in a seal-tight way. Moreover, the plastic end disk should have a connecting contour that is suitable for producing a seal-tight and detachable connection to a connecting element. Such an end disk is disclosed in, for example, DE 199 19 289. Here, the manufacture of a plastic end disk is disclosed that is used for a seal-tight connection to a filter medium. For this purpose, stacked plastic disks are employed that have different thermal properties so that they can be selectively heated by inductive treatment.

DE 101 06 734 discloses a method for producing a connection between a fluid-impermeable plastic material and a fluid-permeable filter material. For this purpose, the plastic end disk is plastified in the area to be connected by an infrared heat source wherein the infrared heat source must have certain predetermined technical features.

A disadvantage of the first plastic end disk is that it must contain metal particles in order to be heatable by the inductive heat source because such plastic end disks are difficult to dispose of. The plastic end disk of the second method must not contain pigments for a colored or black design of the material which pigments have great heat-absorbing properties. This can cause in case of quick and intensive heating exothermal reactions within the synthetic material resulting in destruction of the material. Even without the heat-absorbing materials within the plastic material the radiation intensity that is acting on the plastic material must not be too great because this can cause bubble formation and burns on the surface of the plastic material.

It is an object of the invention to provide a plastic end disk that can be simply and inexpensively manufactured and that enables an especially homogenous plastification in the area of the joining zone at short plastification times. This object is solved by the features of claims 1 and 8.

DISCLOSURE OF THE INVENTION

The inventive plastic end disk comprises two substantially circular cylindrical plastic layers wherein an end face plastic layer of the plastic end disk can be connected to a hollow-cylindrical zigzag-shaped folded filter medium by means of a melting process of the plastic layer at the end face. The plastic layers can be glued or welded to one another, produced in a two-component method or can be simply stacked. In this connection, the plastic layer at the end face is plastified and in the plastified state is pressed onto the tips of the fold ends of the filter medium and hardened thereat. The plastic end disk can be used preferably as a liquid filter but it is also possible to use it as a gas filter. Moreover, the plastic layer at the end face is designed to be substantially transparently for infrared radiation or heat radiation and the plastic layer directly adjacent thereto is designed to be substantially absorbent for infrared radiation. When irradiating with an infrared source, the end face plastic layer is penetrated by the infrared radiation and is heated by excitation of the atoms and molecules. The major portion of the infrared radiation will however penetrate the end face plastic layer and will impinge on the boundary layer to the neighboring plastic layer where it is partially absorbed and partially reflected. The reflected infrared radiation in turn will heat the end face plastic layer from the interior. The infrared radiation proportion that impinges on the interface between the plastic layers heats the boundary layer in the area of the neighboring plastic layer. As a result of the hot boundary layer, there is furthermore heat conduction from the interior into the neighboring plastic layer as well as into the end face plastic layer. The end face plastic layer is preferably of a natural color or is colored with a light-transparent or laser-transparent pigment. With this configuration of the plastic end disk it is achieved that the hottest location of the melting process is located in the interior at the interface between the end face plastic layer and the neighboring plastic layer of the plastic end disk; in this way, the end face plastic layer is very uniformly plastified. This is of great importance for welding it to the terminal edges of the filter medium. In this way, a greater penetration depth and improved processing can be achieved so that an improved seal-tightness results. Moreover, the cycle time can be significantly reduced because the material that is substantially transparent for infra red radiation at great radiation input does have the tendency to form bubbles and the radiation proportion will be better distributed in the plastic end disk. In this way, from the beginning a greater radiation intensity can be employed in the process which leads to a reduction of the processing time. Moreover, the main heating zone is within the area of the boundary layer so that the remainder of the neighboring plastic layer remains shape-staple thus improving handling.

According to an advantageous embodiment of the invention the plastic end disk is produced by a two-component injection molding process from a thermoplastic synthetic material. In this connection, preferably first the plastic layer that absorbs infrared radiation is injection molded and, subsequently, the end face plastic layer that is substantially transparent for infrared radiation is injection molded onto the absorbing layer. This manufacturing process is sufficiently perfected and provides great advantages in regard to process safety.

In this connection. it is advantageous when the end face plastic layer is comprised of a substantially glass fiber-free polyamide and the neighboring plastic layer having absorbing properties is comprised of a glass fiber-reinforced polyamide to which dark heat-absorbing particles are added. As a result of the embodiment of the end face plastic layer of polyamide that is essentially free of glass fibers, the advantage results that the plastification process can be performed very uniformly and the attachment to the zigzag-shaped folded ends of the filter medium is particularly intimate. The required stability of the plastic end disk is then ensured by the embodiment of the neighboring plastic layer from glass fiber-reinforced polyamide.

According to an advantageous embodiment of the invention the end face plastic layer has at a radial end an axially projecting annular collar. The latter can be arranged at the outer radial end or the inner radial end of the end face plastic layer. The annular collar extends axially away from the filter medium and forms a sealing contour that matches a corresponding sealing counterpart. This sealing counterpart can be a central tube of the housing or of the filter element or can also be a contact socket of the housing. The sealing contour is formed as an integral part of the annular collar.

It is moreover possible that the plastic layer neighboring the end face plastic layer furthermore forms a functional element, in particular a liquid outlet. The plastic layer neighboring the end face plastic layer is the side of the plastic end disk facing away from the filter medium wherein it is possible in this way that this plastic layer also serves for centering and fixation of the filter element in a housing or forms a through opening and a thread for a discharge screw.

According to an advantageous embodiment of the invention the side of the neighboring plastic layer that faces the end face plastic layer has a surface area-enlarging relief contour. This can be, for example, in the form of an audio record contour or in the form of a circumferentially extending wave line or sawtooth line. Since the two plastic layers are produced by a two-component method, the end face plastic layer has therefore a matching surface profile. By enlarging the surface area by means of the surface area-enlarging relief contour an even better heat introduction by means of the infrared radiation into the interface between two neighboring plastic layers results so that in this way the processing time is further significantly reduced.

For producing a filter element in connection with the plastic end disk according to the invention, in a first step the first plastic layer that is essentially transparent for infrared radiation is trans-irradiated by the infrared radiation source. The infrared radiation source can be a laser or an infrared radiator. The infrared radiation penetrates the first end face plastic layer that is substantially transparent and thus impinge on the second plastic layer that is substantially absorbent for infrared radiation. At the interface between the two plastic layers a great heat above the melting temperature develops by absorption of infrared radiation so that the boundary layer begins to plastify. As a result of the radiation of infrared radiation at the boundary layer and a minimal heating of the transparent plastic layer upon trans-irradiation, said plastic layer is plastified from the interior to the exterior uniformly and homogeneously. In a second step, the infrared radiation source is removed and the adjacently positioned terminal edges of his zigzag-shaped folded fluid-permeable filter material are pressed into the still melted plastified area of the first plastic layer. This position is maintained until a fixed connection of the terminal edges of the filter material with the synthetic material in the pressed-in state is achieved. By means of the special design of the plastic end disk, it is possible to work with a high radiation intensity of the infrared radiation source so that extremely short cycle times will result.

Aside from the claims, these and further features of preferred embodiments of the invention result also from the description and the drawing wherein the individual features, taken alone or several combined in the form of sub combinations, can be realized in the embodiment of the invention or in other fields and can represent advantageous as well as independently protectable embodiments for which protection is sought herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention are described in the drawing with the aid of schematic embodiments. It is shown in:

FIG. 1 a liquid filter in section view; and

FIG. 2 a detail view of the plastic end disk in a detail illustration.

EMBODIMENT(S) OF THE INVENTION

The FIG. 1 shows a liquid 10, in particular fuel filter, with a cup-shaped housing 11 provided with an intake 12 and an outlet 13. The outlet 13 is arranged centrally on the end face of the cup-shaped housing 11 and the intake 12 is arranged concentrically about the outlet 13 distributed onto several openings. In the interior of the cup-shaped housing 11 a filter element 14 is arranged that separates seal-tightly an unfiltered side 30 from a filtered side 31. In the lower area of the cup-shaped housing 11 the filter element 14 is secured axially in the housing 11 by a bottom member 15. The bottom member 15 has a support for the filter element 14 as well as an inner thread 16 that provides at the bottom of the cup-shaped housing a receptacle for a drainage screw 17. When using the liquid filter 10 as a fuel filter, especially a diesel fuel filter, in the lower area of the cup-shaped housing 11 water that is heavier than fuel will collect that is then drained by means of the drainage screw 17 from the cup-shaped housing 11. The cup-shaped housing 11 is closed off by a metallic cover plate 18. This cover plate 18 has a centrally arranged threaded receptacle 19 that receives a threaded socket of a counterpart, not illustrated, for example, a fuel assembly or a cylinder block. The cover plate 18 is secured to the housing wall of the cup-shaped housing 11 by a securing plate 20 wherein the securing plate 20 on the one hand is connected to the cup-shaped housing 11 by crimping in a seal-tight and non-detachable way and on the other hand secures the cover plate 18 by a fold also in a seal-tight way. In the cover plate 18 the intake and outlet openings 12, 13 of the liquid filter are arranged also. The securing plate 20 has axially outwardly a circumferential groove for receiving a seal 21 that serves for sealing the liquid filter 10 relative to the counterpart. The filter element has a hollow-cylindrically arranged preferably zigzag-shaped folded filter medium 20 made of filter paper or a non-woven filter material or a synthetic material or a mixture of all of the above and is supported by an inwardly positioned support tube 23 against collapse. The filter element 14 is closed at the bottom by a closed lower end disk 24 that is made of a thermoplastic material that is substantially transparent for infrared radiation. The end disk 24 is welded by an infrared welding method to the bottom member 15 that is substantially absorbent for infrared radiation. It is however also conceivable to provide a nitrile rubber end disk that rests on the bottom member 15 or is connected to it by an adhesive. On the opposite end face the filter element 14 has an open end disk 25 which has an end disk part 26 and a sealing part 27. The sealing part 27 is in the form of an annular collar 33 that axially extends away from the filter medium. It ends in a T-shaped member wherein one end of the T member provides a radial seal 28 relative to a vertical extending circumferential edge of the cover plate 18 and the opposite end of the T member of the sealing part 27 rests axially against a horizontal contact surface of the cover plate 18. In this way, on the one hand an axial sealing action results and on the other hand an improved radial sealing action at the radial seal 28, caused by means of a certain axial compression, as a result of a minimal rotation of the T shaped leg of the annular collar 33.

FIG. 2 shows a detail in the area of the plastic end disk. Components that correspond to those of the preceding figure are identified with same reference numerals. The two-layer configuration of the plastic end disk 25 can be seen clearly. The end face facing the filter medium 22 has a plastic layer 32 that is transparent for infrared radiation which completely receives the filter medium 22. The transparent plastic layer 32 has in the radial inner area an annular collar 33 a that continues as a sealing part 27. An absorbent plastic layer 34 is connected to the transparent plastic layer 32 and has at its radial inner end also an annular collar 33 b that is shaped so as to match the shape of the annular collar 33 a and supports it in a shape-stabilizing way. On the interface between the transparent plastic layer 32 and the absorbent plastic layer 34 there is a sawtooth contour 35. It serves for providing better absorption and reflection of the infrared radiation passing through the transparent plastic layer 32 so that the plastification process in the area of the interface happens faster. 

1.-8. (canceled)
 9. A plastic end disk for a hollow-cylindrical filter element, the plastic end disk comprising: an end face plastic layer and a neighboring plastic layer; wherein the end face plastic layer is substantially transparent for infrared radiation; wherein the neighboring plastic layer is substantially absorbent for infrared radiation; wherein the plastic end disk is adapted to be connected to a hollow cylindrical zigzag-shaped folded filter medium by plastifying the end face plastic layer by infrared trans-irradiation.
 10. The plastic end disk according to claim 9, injection-molded by a two-component injection process from a thermoplastic synthetic material.
 11. The plastic end disk according to claim 10, wherein the end face plastic layer is comprised of a substantially glass fiber-free polyamide and the neighboring plastic layer is comprised of a glass fiber-reinforced polyamide comprising dark heat-absorbent particles.
 12. The plastic end disk according to claim 9, wherein the end face plastic layer has an axially projecting annular collar forming a sealing contour relative to a matching sealing counterpart.
 13. The plastic end disk according to claim 12, wherein the axially projecting collar is positioned at an inner radial end of the end face plastic layer.
 14. The plastic end disk according to claim 9, wherein the neighboring plastic layer has a functional element.
 15. The plastic end disk according to claim 14, wherein the functional element is a drainage for liquid.
 16. The plastic end disk according to claim 9, wherein a side of the neighboring plastic layer that is facing the end face plastic layer has a surface area-enlarging relief contour.
 17. A filter element comprising a filter medium and a plastic end disk according to claim 9 connected to the filter medium.
 18. A method for providing a fixed, seal-tight connection between adjacently positioned terminal edges of a zigzag-shaped folded fluid-permeable filter medium and a plastic end disk according to claim 9, wherein the method comprises the steps of: trans-irradiating with an infrared radiation source an end face plastic layer that is substantially transparent for infrared radiation, wherein the infrared radiation is absorbed in a neighboring plastic layer substantially absorbent for infrared radiation and neighboring the end face plastic layer so that a portion of the neighboring plastic layer and a portion of the end face plastic layer are completely melted; removing the infrared radiation source; pressing the terminal edges of the filter medium into a melted area of the end face plastic layer; securing the filter medium in the pressed in position in the end face plastic layer until a fixed connection of the filter medium and the end face plastic layer has been formed. 